Palatinitol is a sweetening agent of low caloric mass and low cariogenicity which up to now is obtained by catalytic Hydrogenation at neutral pH of isomaltulose or .alpha.-D-glucopyranosyl-(1.fwdarw.6)-D-fructose.
Isomaltulose is itself obtained by enzymatic isomerization, using a saccharose glysosyl transferase, saccharose or .alpha.-D-glucopyranosyl-(1.fwdarw.2)-.beta.-D-fructofuranoside.
Therefore, it is saccharose which constitutes the raw material for obtaining palatinitol, a mixture in roughly equimolecular proportions, of .alpha.-D-glucopyranosyl-(1.fwdarw.6)-D-sorbitol (GPS or isomaltitol) and .alpha.-D-glucopyranosyl-(1.fwdarw.6)-D-mannitol (GPM).
Palatinitrol, which is also called isomalt, is in particular marketed by the Company Suddeutsche Zucker AG under the name Palatinit.RTM..
Among other documents which concern the obtaining and properties of palatinitol the following work can be referred to: "Alternative Sweeteners" published in 1986 by LYN O'BRIEN NABORS, chapter 11, pages 217 to 244.
Concerned to develop a process which allows palatinitol to be obtained from a raw material other than saccharose, the Applicant Company has noticed that this goal could be achieved by a process using isomaltose or .alpha.-D-glucopyranosyl-(1.fwdarw.6)-D-glucose.
In accordance with the present invention, palatinitol is obtained thanks to a process characterized in that
in a first stage, the epimerization of isomaltose is carried out under conditions which allow a mixture of .alpha.-D-glucopyranosyl-(1.fwdarw.6)-D-mannose and isomaltose to be obtained, PA1 in a second stage, the epimerized mixture is depleted of isomaltose so as to obtain a mixture containing a roughly equimolecular proportion of .alpha.-D-glucopyranosyl-(1.fwdarw.6)-D-mannose and isomaltose, PA1 in a third stage, catalytic hydrogenation is carried out on this mixture.
If it is reasonable to imagine that palatinitol may be obtained from saccharose, the person skilled in the art could in no way expect that this same palatinitol might be obtained from isomaltose which is obtained from glucose and thus from diverse and various starches.
In fact, in the first case, saccharose, the structural formula of which includes a fructose unit, will produce, in a known fashion by enzymatic isomerization, the corresponding ketose i.e. isomaltulose.
And it is known to the person skilled in the art that the hydrogenation of such a ketose leads to the formation of the two corresponding itols in approximately equimolecular proportions. Therefore, the fact that the formula of saccharose is related to that of palatinitol allows the result to be anticipated.
However, the process according to the invention does not implement a starting product whose formula is related to that of the sought palatinitol. In fact, isomaltose as well as glucose and starch have a structure which does not contain a fructose unit and is therefore far from being related to that of palatinitol.